Abrasive sheet support system



Jan. 26, 1965 REAMES 3,166,877

ABRASIVE SHEET SUPPORT SYSTEM Filed Feb. 18, 1963 INVENTOR LEONARD (JHis/W55 BY ML o/v, 5E7 n5 & C 616 ,qrrok/vevs United States Patent3,166,877. A R S VE SHEET SUPBQR S fiT M Leonard W. Rearnes, Howell,Mich, assignor to Edward J. Sopcalr, Howell, Mich, and Thomas L; Draper,Birmingham, Mich.

Filed Feb. 18, 19 63, Ser. No. 259,276

' 3 Claims, (Ci. 51-378) This invention relates to the abrasive art; andmore particularly to a support system for abrasive sheets for use onrotary abrading machines.

The problem In the grinding or dressing of surfaces such as of metalcastings, automobile bodies for repainting and the like, the rotaryabrasive machine has been found to be particularly desirable. The rotaryaction tends to render the abrasive self-cleaning by rejecting thematerial removed from the surface and thus reduces the clogging of theabrasive grit that would otherwise occur.

Early abrasive sheet support systems merely comprised a sheet ofabrasive material cemented to a rubber backing disc. However, becausethe rubber backing disc acted as a heat insulator, early cloggingresulted from the fact that paint and other materials removed from asuriace were rendered gummy by the heat and thus caused early cloggingthus overriding the advantage of circular action.

One advance in the art provided a ribbed backing member for the abrasivesheetfioatably supported between the abrasive sheet and a rubber drivedisc, so that the backing sheet could move relative to the abrasive andthus bring different grains into contact with the work surface uponrepeated application of the abrasive thereto. This is set forth in ourcopending application Serial Number 259,109, filed February 18, 1963,which describes a novel backing disc and its use in the typical priorart mounting system.

However, such typical prior art mounting system as will be hereinafterdescribed was characterized either by:

(a) A substantial number of parts requiring consider- I able dexterityby the Workman in replacing the abrasive sheet when it' wore out; or

(b) Welding parts together to reduce the total number. However, thisrequired discarding the more costly and essential part, namely, therubber drive disc, when replacingthe backingdisc. ii

Accordingly, an important advance inthe art would be provided by anovelsupport system for rotary abrasive discs characterized by a minimumof parts yet providing for the replacement of the separate elementswithout discarding any other element.

Objects Accordingly, an important object of the present inven tion is toprovide a novel support system for a rotary abrasive disc. t

A further object is to provide a novel support system for a rotaryabrasive disc characterized by improved *ease ofassembly and reducednumber of Working parts.

A still fr rther object is to provide a nove support system'for a rotaryabrasive disc characterized by handling teristic of analogous units ofthe prior art.

Other objects of this invention will appearin the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

Ilie drawings 1 is a section view .of-a typical rotary abrasive sheetsupport system of the prior art;

FIGURE 2 is a section View similar to FIGURE 1, but showing a preferredembodiment of the present invention; and

FIGURE 3. is a section view of a second embodiment of the invention.

Before explaining the present invention in detail it is to be understoodthat the invention is'not limited'in its application to the details ofconstruction and arrangement of parts illustrated in. the accompanyingdrawings, since the invention is capable of other embodiments and ofbeing practiced or carried out in various ways Also, it is to beunderstood that the phraseology 9r terminology employed herein is forthe purpose of description and not of limitation.

v The environment The environmental surrounding of the present inventioncomprises an electric motor driven and generally handheld grinder orabrasive machine. Such a machine typically includes a driving motormounted within a die cast aluminum housing or equivalent. handle orhandles are formed on the housing so that an operator can pick up theunit and manipulate it over a surface to be dressed, such as anautomobile tender in repairing the same. A drive shaft is journaled inthe housing and is suitably geared to the motor. I

The shaft of the machine has an extending stub and this is designatedby'the reference numeral 10 in FIG- U E 1 of the d aw n GU E 1 lu t te eknow structure which has heretofore-been employed, but' upon which thepresent invention provides an advance in the art.

A typical prior structure Referring now to FIGURE 1 in further detail,it will be noted that stub 10 is provided-with an axially extendingthreaded bore 12 to receive a cap screw'14 used to hold the grindingassembly to the end of the stub shaft 10.

The general components of the system It will be noted that a rubberdrive washer 16 of substantial body andthickness is provided with ametal insert 1.8 at the center. The insert 13 comprises a tubular sleeveflanged at the top end as at 20. The insert 18 is joined as byvulcanizing in the center hole of the rubber 'drive disc 16. i

It will be noted that the body of the cap screw 14 is inserted throughthe bore of the insert 18"'for as'seinbly inherent in either of thesearrang t wm be a gh hereinafter.

It will be noted that an abrasive sheet 26 of circular form and havingan appropriate centerhole is held between the cap 240i js crew 1 4andthe topside of the spacer 22. w i

The backing disc, one form being disclosedinour copending applicationSerial Numberi25 9,ll09,'filed;l?ebit ary 18, 19.63, is designated28 andis (if-generally circular configuration. The disc 2 8 hasacenter.hole'sliyvn eby it is fitted "into the "spacer22.forretentionagainst-ahial movement. 'It mightbe stated that 'the'spacer 22 is flanged over'on one side or'the other after insertionthrough the center hole 30 .Ot-the disc 2 8 to assemble the parts. Itwill be noted that thehole fillis slightly larger than the bight of thespacer 22, so that the disc I washer 16 by floating on the spacer 22 inthe space between the abrasive sheet 26 and drive washer 16. It will beunderstood from the foregoing that the sheet 26 and washer 16 movetogether but can rotate relative to disc From the foregoing it will beunderstood that when the workman presses the abrasive sheet against awork surface, the drive disc presses against the back of disc 28 on oneside and the work presses sheet 26 against the disc on the other side tolock all 3 elements together.

Advantage of this arrangement is that every time a workman lifts theunit .away from the work surface, the backing disc 28 can move slightlyrelative to the abrasive sheet 26 and the drive disc 16, so that on nextcontact with the work, different abrasive grain will be forced intocontact with the work surface and therefore give the grain previouslyworking, a chance to unload. As discussed above, the backing disc formsa subject of our copending application and therefore a more detaileddescription is not set forth herein. It is sufiicient to note that thebacking disc 28 is provided with radially extending ridges to provideradial lines of contact between the abrasive grit and the work, andthese change upon release of pressure as set forth above.

This prior art structure, as will be noted from the foregoingdescription, could be made according to one of the following optionalarrangements:

(A) A drive washer 16, spacer 22 and disc 28, and abrasive sheet 26 canbe separately assembled on the cap screw 24. This provided the greatestnumber of parts, namely, four as follows:

viding one less part, to wit:

(1) Washer 16-spacer 22-disc 28 as a single assembly;

(2) Abrasive sheet 26; and

(3) Cap screw 24,

It will be noted that this arrangement provides a lesser number ofparts, thus giving greatest economy of operator time'for changing theabrasive sheet but a distinct disadvantage from a cost standpoint. Thus,because the spacer 22 and drive Washer 16 are an integral unit by spotwelding replacement of the backing disc 28 necessarily entails loss ofthe drive washer 16.

The present" invention provides a distinct advance in the art ovcreachof the foregoing prior art arrangements, and a full description will nowbe provided.

The inventive embodiment FIGURE 2 In accordance with the presentinvention, provision is made for changing the abrasive sheet with aminimum disassembly of parts, and the replacement of the backi ing discwithout throwing away the rubber drive washer; thus providing in oneadvanced unit, the advantages of both of the above arrangements of theprior art, but without any of the disadvantages.

' Drive washer 0f FIGURE 2 The present invention embodies a rubber drivewasher as described in the prior art; however, because of its differentconfiguration, it will be provided with a different reference number.Thus, in the embodiment of FIG- URE 2, the drive disc is designated bythe reference numeral 32. The disc 32 has a larger center hole 34 than16 previously discussed, to accommodate the larger diameter of theinsert 34. The insert 34 has a tubular body portion 36, and an annularbase flange 38 having a threaded opening 40 centrally thereof.

Exlcnsion shaft In this embodiment of the invention, as distinguishedfrom the prior art of FIGURE 1, note that an extension shaft 42 isutilized that is provided at its top end with a threaded stud portion 4that is turned into the thread opening it? of flange .38 of insert 34.The remaining details of this shaft include opposed flats 46 forapplication of a wrench and a threaded stud portion 48 at the bottom. Bythe bottom threaded stud 48, the unit can be attached to the stub shaftof an abrasive machine in the manner of FIGURE 1.

To review a bit, it should be pointed out that joinder between insert34- and the drive washer 32 is made as by vulcanizing.

Note that the interior of the insert 34 is threaded with a known type oflocking thread 50.

Disc holder 0) FIGURE 2 An important aspect of the present inventionresides in the attachment of the backing disc, designated 28, becausethe same as previously described. This is effected by means of a discholder designated by the reference numeral 52 that is threaded into thethread 58 in locking relation.

Disc holder 52 includes a tubular body member 54, externally threadedwith a locking thread to lock into the previously mentioned lockingthread it). The holder 52 is provided with a top annular flange 56. itwill be noted that the exterior thread 55 on body member 54 extends onlypart way up, so that an annular washer 58 when tightened thereon will bestopped in spaced relation to the top flange 56.

The disc holder 52 is assembled to the backing disc 28 by inserting thebody 54 through the center hole 30 of the backing disc and thenthreading on the annular washer 58 in locking relation. Disassembly ofthis unit is the reverse. Further assembly comprises threading thebottom exposed portion of the thread 55 into the thread 5th until thewasher 58 bottoms on the top flange 60 of insert 34 to provide a locked,assembled relation of parts.

Abrasive sheer retainer 0 FIGURE 2 As shown in the upper portion ofFIGURE 2, the abrasive sheet retainer 62 takes the form of what might bedescribed as an internal thread cap screw. Thus, the unit d2 includes atubular body 64 internally threaded as at 66 whereby it is threaded ontothe upper portion of threaded stud 44 of the shaft 42, that waspreviously threaded through center hole 40 of washer 32.

Final assembly is made by laying the abrasive sheet 26 on top of thebacking disc 28 with the center hole aligned, and then inserting andtightening the capped retaincr 62.

Regarding the foregoing embodiment, it is noted that the drive washer 32and backing sheet disc 28 are dished slightly at the center, so thatwhen final assembly is made, the top flange 68 will lie slightly belowthe working level of the abrasive sheet as in FIGURE 1, so that only theabrasive grit will contact the work and the top of the cap member 62therefore does not engage the work to prevent scarring.

Changing abrasive FIGURE 1 From the foregoing, it will be noted thatchanging the abrasive sheet 26 merely involves removal of the retainer62; lifting off the sheet; and replacing. The drive washer 32 is neverremoved, nor is its relationship with the backing disc 28 disturbed.

It will be noted however that if replacement of the backing disc 28becomes necessary, this can be done very easily by merely removing thedisc holder 52; the washer 58; and reassembling. Note that thisoperation is effected quickly and without loss of the more expensivedrive Washer 32.

Thus, a substantial advance in the art is provided.

The inventive embodiment of FIGURE 3 The embodiment of FIGURE 3 utilizesa cap screw in accordance with the prior art; but, like FIGURE 2,

overcomes the disadvantages of the prior art and functions in a mannergenerally analogous to the embodiment of FIGURE 2.

A complete description of the FIGURE 3 embodiment now follows:

This embodiment of the invention, mounts directly to the end of the stubshaft and utilizes a cap screw 14.

Drive washer of FIGURE 3 Disc holder 0] FIGURE 3 A disc holder,designated by the reference numeral 84, is threaded into the thread 7 6in locking relation. The disc holder 84 includes an outer tubular bodymember 86, externally threaded as at 88, with a locking thread to lockto the previously mentioned locking thread 76. This unit is providedwith an annular, radial top flange 90. Inside the body 86, there ispress fitted and locked against rotary movement, as by splines, atubular body member 92, having a top flange 94. It will be noted thatthe flanges 90 and 94 are axially spaced to accommodate the backing disc28 for rotation in the U-shaped section channel formed therebetween. Theunit 84 is threaded into the thread 76 and both exterior body member 86and interior body member 92 bottom on the base flange 78 to preserve thechannel space between 90, 94. Thus the backing disc 28 and the rubberdrive washer 70 are an assembled unit for operation, but can be disas- 6sembled for replacement of the backing 28 should this become necessary.

Assembly of FIGURE 2 To assemble the system for operation to the stubshaft iii, the cap screw 14 is inserted through the hole in the abrasivesheet 26 and then through the disc holder 84 which with attached disc28, and then through rubber drive washer 7t and then threaded into thebore 12 of the shaft 10. The same principle of operation is provided asin FIGURE 2. Thus, it will be noted that case of abrasive discreplacement is provided and that the backing member 28 can be replacedwhen necessary with a minimum expenditure of time and without otherparts replacement.

What I claim is:

1. A support system for securing a circular abrasive sheet to a threadedshaft comprising an annular drive washer of resilient material, aninteriorly threaded insert fixed to said washer at the center thereof,disc holding means including a pair of telescopically assembled axiallybored elements having concentric axially spaced flanges definingtherebetween an outwardly opening channel, one of said elements beingexteriorly threaded for threaded assembly into said insert, a backingdisc having a central aperture through which one only of said elementsprojects to entrap said disc between said flanges with said discoverlying said drive washer, and an abrasive sheet retainer having aradially enlarged flange for confining a central portion of saidabrasive sheet against said disc holding means and an axial projectionextending through said disc holding means for, threaded engagement withsaid threaded shaft.

2. A support means as defined in claim 1 wherein the disc holding meansincludes a first element provided with a top annular flange and anexternally threaded body, and a second element in the form of a washerthreaded onto the body of the first element, the first element flangeand the washer defining an outwardly opening channel therebetween.

3. A support system as defined in claim 1 wherein the disc holding meansincludes a first element having a peripheral flange and an elongatedaxial extension and a second element including a peripheral flange andan exteriorly threaded axial extension interiorly bored to receive theextension of the first element therethrough, in sliding relationshiptherewith.

References Cited in the file of this patent UNITED STATES PATENTS2,902,799 Beck Sept. 8, 1959

1. A SUPPORT SYSTEM FOR SECURING A CIRCULAR ABRASIVE SHEET TO A THREADEDSHAFT COMPRISING ANANNULAR DRIVE WASHER OF RESILIENT MATERIAL, ANINTERIORLY THREADED INSERT FIXED TO SAID WASHER AT THE CENTER THEREOF,DISC HOLDING MEANS INCLUDING A PAIR OF TELESCOPICALLY ASSEMBLED AXIALLYBORED ELEMENTS HAVING CONCENTRIC AXIALLY SPACED FLANGES DEFININGTHEREBETWEEN AN OUTWARDLY OPENING CHANNEL, ONE OF SAID ELEMENTS BEINGEXTERIORLY THREADED FOR THREADED ASSEMBLY INTO SAID INSERT, A BACKINGDISC HAVING A CENTRAL APERTURE THROUGH WHICH ONE ONLY OF SAID ELEMENTSPROJECTS TO ENTRAP SAID DISC BETWEEN SAID FLANGES WITH SAID DISCOVERLYING SAID DRIVE WASHER, AND AN ABRASIVE SHEET RETAINER HAVING ARADIALLY ENLARGED FLANGE FOR CONFINING A CENTRAL PORTION OF SAIDABRASIVE SHEET AGAINST SAID DISC HOLDING MEANS AND AN AXIAL PROJECTIONEXTENDING THROUGH SAID DISC HOLDING MEANS FOR THREADED ENGAGEMENT WITHSAID THREADED SHAFT.